I dont agree with many things apple does at all, and I also think their password manager has flaws like revealing usernames without authentification.
It is pretty handy though, to have a file where the entries are stored unencrypted, and if the password manager detects an entry it prompts to decrypt exactly that field, maybe with a fingerprint.
KeepassDX needs to run in the background and be completely unlocked to even detect apps or password fields.
Do you know any existing app that can do this?
Well, only if you host it in the cloud. Not if you host it at home, for example.
I think what they meant is that one option uses network connectivity while the other functions entirely offline
Which would make it hardly accessible outside of your home. Still not locally saved as well. And imho if he is not sure which password manager he should choose, he should maybe not self host just yet.
Bitwarden keeps a local encrypted copy of the database and only connects to the server for synchronisation.